Reproduction Flashcards
what are male gonads called?
testes
where is sperm produced?
in the seminiferous tubules of the testes
what are spermatogonia?
spermatogonia are located in the seminiferous tubules of the testes (where sperm is made).
spermatogonia arise from the epithelial tissue to become spermatocytes, spermatids and spermatozoa
what do sertoli cells do?
they surround and nurture spermatocyte and spermatids
they are stimulated by FSH
What do leydig cells do?
release testosterone when stimulated by LH
What is the function of testosterone?
its the primary androgen (male sex hormone) and stimulates the germ cells to become sperm. its also responsible for secondary sex characteristics (pubic hair, enlargement of the larynx, growth of penis and seminal vesicles).
- it also helps with the closure of epiphyses of the long bones , ending growth in stature.
what happens when a spermatid becomes a spermatozoon?
it loose its cytoplasm and form a head, mid piece and a tail
what does the head contain?
nucleur material and acrosome (lysosome like enzymes which will penetrate the egg)
what does the mid piece have?
lots of mitochondria to help provide energy for movement
which piece enters the egg?
only the nucleur portion
where does the spermatozoon go to mature?
epididymis!
what happens to spermatozoa upon ejaculation?
propelled through the vas deferent into the urethra and out of the penis
what is semen?
mixture of spermatozoa and fluid that leaves the penis
-its composed of fluid from the seminal vesicles, the prostate, and bulbourethral glands (cowpers glands)
where do the spermatozoa become activated for fertilization?
in the vagina a process called capacitation occurs.
when does oogenesis begin?
in the ovaries of the fetus . alll the eggs of the female are arrested as primary oocytes at birth.
what happens at puberty?
FSH stimulate growth of granulosa cells around the primary oocyte. which will secrete viscous substance around the egg called zone pellucida. the structure @ this stage is the primary follicle.
how does the secondary follicle form?
theca cells grow around the follicle . upon stimulation by LH, theca cells secrete androgen which is converted to estradiol (type of estrogen) by the granulosa cells in the presence of FSH and is secreted into the blood.
Estradiol will prepare uterine wall for pregnancy. the follicle grows and bulges from the ovary
what happens just before ovulation?
estradiol levels rise rapidly, which cause a dramatic increase in LH secretion. this increase is called luteal surge
what happens in the luteal surge?
the luteal surge results from a positive feedback loop of rising estrogen levels which results in increase LH levels , which increase estrogen. the luteal surge causes the follicle to Burst , releasing the egg (now a secondary oocyte).
what happens to the released egg (secondary oocyte)?
egg is swept into the Fallopian tube or oviduct by fimbriae. the remaining part of the follicle becomes the corpus luteum
what does the corpus luteum do?
it secretes estradiol and progestrone throughout pregnancy or in the case of no pregnancy: for about 2 weeks until it degrades into corpus albicans
how often does this cycle repeat itself?
28 days ( called the menstrual cycle)
what are the three phases of the menstrual cycle?
1) the follicular phase- begins with development of the follicle and ends @ ovulation
2) luteal phase: begins with ovulation and ends with degradation of the Corpus luteum
3) flow : shedding of the uterus lining lasts ~5 days
Where does fertilization take place?
in the Fallopian tubes. the enzymes in the acrosome are released upon contact with the egg.
cell membranes of the sperm and the oocyte fuse upon contact and sperm nucleus enters the cytoplasm of the oocyte. this entry will cause cortical reaction, which prevents other sperms from fertilizing the same egg.
now the oocyte goes through another division ( second meiotic division) to become an ovum and it releases a second polar body
when does fertilization occur?
when the nuclei of the ovum and the sperm fuse to form a zygote.
cleavage
cleavage starts while the zygote is still in the Fallopian tube. the zygote foes thru many cycles of mitosis - when its 8 or more cells : its called a morula. (at this stage they are totipotent)- they can express any genes ( so any of these 8 cells can make its own individual).
what happens to the morula?
the cells continue to divide to form a hollow ball filled with fluid : called a blastocyst.
what does the blastocyst do?
it will lodge onto the uterus in a process called implantation on about 5-7 days after ovulation.
what kind of cells is the blastocyst made of?
embryonic stem cells: which can develop into MOST of the types of cells in the human body
what happens at implantation?
female is said to be pregnant
- upon implantation, egg secretes HCG ( human chorionic gonadotropin)
what is the function of human chorionic gonadotropin that’s secreted by the impacted egg?
it prevents degeneration of corpus luteum and maintains the secretion of estrogen and progesterone.
HCG in the blood and urine is the first sign of pregnancy.
what does the placenta do?
so the placenta forms from the tissue of the egg and from the tissue of the mom and takes over the job of hormone secretion.
- it reaches full development by end of the first trimester
and begins secreting its own estrogen and progesterone
what is determination?
- process where a cell becomes committed to a specialize developmental path.
- become determined to give rise to a specialized tissue early on.
- fate is determined earlier on, but that same cell docent usually differentiate into specialized tissue until much later at the end of the developmental process.
What is gastrulation?
where a gastrula is formed. ( cells begin to move about the embryo for the first time) - this is after the second week after fertilization
During gastrulation which 3 germ layers are formed?
1) ectoderm
2) mesoderm
3) endoderm
Fate of the ectoderm…
epidermis of the skin, nervous system, sense organs
fate of mesoderm
skeleton, muscles, blood vessels, heart, blood, gonads, kidneys, dermis of the skin
fate of endoderm
lining of digestive and respiratory tracts, liver, pancreas, thymus , thyroid
in the third week the gastrula develops into what?
neurala in a process called neurulation. this is where notochord induces the overlaying ectoderm to thicken and form the neural plate.
the notochord will disintegrate, while the neural tube will form from the neural plate.
the neural tube will become the spinal cord, brain, and most of the nervous system.
what is apoptosis regulated by?
protein activity ! not transcription or at the translation process!
the proteins involved in apoptosis are present but they are inactive in a normal healthy cell.
